Combination locking push button and adjustment knob



N. M DONALD Filed Feb. 24, 1953 COMBINATION LOCKING PUSH BUTTON AND ADJUSTMENT KNOB June 26, 1956 PO TENT/OME 75/? IN V EN TOR. DUNCAN N. MACDONALD A 7' TORNE V 3 'M/ VII COMBINATION LOCKlNG PUSH BUTTQN AND ADJUSTMENT KNOB Duncan N. MacDonald, Arcadia, Calif, assignor, by mesne assignments, to Consolidated Electrodynamics Corporation, Pasadena, Calif., a corporation of California Application February 24, 1953, Serial No. 338,343

7 Claims. (Cl. 200-172) This invention relates to an improved combination locking control and switching device for making angular adjustments to rotary components of such instruments as potentiometers, variable condensers and the like.

Most complex electronic devices, mass spectrometers and oscillographs, for example, include numerous components which must be adjusted within narrow ranges of value both absolutely and in relation to each other. Often a number of such adjustments must be made before each major test and, if the results of those tests are to be valid, they must not be disturbed by such means as vibration or accidental contact in the course of the operation of the eqiupment. In addition, these adjustments must be made with the concurrent use of means of standardization such as meters which are incorporated into the circuit during the adjustment operation and are cut out of the circuit after the adjustment is completed.

A definite sequence is necessary for each operation. First, the standardizing devices must be switched into the circuit; second, the adjustment is made by rotating the adjustable control, and third, the standardizing devices are switched out of the circuit. Any other sequence will not produce the necessary results. In existing apparatus such a technique requires a switch to connect the standardizing devices into the circuit and a separate knob for adjustment. On instrument panels already crowded with other objects, these extra switches or knobs are spacewasting and confusing. Moreover, it is possible for the adjusting knobs to be turned before standardizing devices are switched into the circuit and even possible for the wrong knob to be turned without the operator noticing his error. In addition, the adjustment knobs which customarily protrude from the panel may later be disturbed by accidental contact or vibration and the change in setting may go entirely undetected unless the test results later appear to be entirely inconsistent. Such a situation is intolerable when a testing device is mounted in the nose of a combat type airplane, for instance, and personnel and equipment are exposed to perilous conditions to obtain data. It is of supreme importance then that adjustments remain undisturbed and not be subject to change during their normal use.

The present invention provides a means of solving these problems. It is a control assembly which can be retated easily when the control knob is pressed toward the panel but which has friction means behind the panel or case which will inhibit rotation unless the knob is pressed in, making disturbances of the final adjustment by vibration, shock, or accidental contact a virtual impossibility. The invention also includes switching means which are actuated when the knob is pressed in. The switch or switches are conected to the testing or standardizing instruments and are actuated when the adjustment knob is pressed in. This action simultaneously permits rotation of the knob and creates the proper sequence of operations for adjustment of the component. This reduces the units required on the panel by one half, allows two operations to be performed simultaneously and with Patented June 26, 1956 one hand, eliminates any chance of an improper sequence of actions, and provides a locking device which prevents later disturbances of the adjustment. The testing circuit is switched in when the knob is pressed and remains in the circuit while the knob is rotated. Releasing the knob cuts out the testing equipment and engages the knob with the panel or case so that there is only a negligible danger of an undesired disturbance of the adjustment.

This invention is not to be confused with common detent handles, particularly those which rely on notched means to retain a desired setting. This device utilizes a friction lock which can assume any of an infinite number of positions and is not limited by a finite number of notches. For fine adjustments a notched lock is useless. Nor is the present invention to be confused with motionactuated braked operators since the freedom of the latter to rotate depends upon overcoming by one method or another such frictional or spring-loaded means as are provided to inhibit rotation. The present device is intended to be operable only when the friction is relieved by axial pressure on the control knob at which time it also changes the circuitry of the device which is to be adjusted. Were this a motion controlled brake, the friction would have to be so light as to give no guarantee against accidental disturbances, or if stronger, be operable only With great effort due to an excessive frictional resistance. It is further differentiated from any prior device by its unique provisions for switching standardizing means into external circuits in a correct sequence. The locking arrangement is such that an infinite number of adjusting positions may be assumed and rotation is prevented unless the arrangement is unlocked. This invention thus provides a combination locking push button and adjustment control.

The invention will be completely understood from the following description of its presently preferred embodiment with reference to the drawings, in which:

Fig. l is a plan view, partly in section; and

Fig. 2 is a sectional elevation along line 22 of Fig. 1.

In the preferred embodiment shown in Figs. 1 and 2, the control assembly is entirely self-contained and adapted to be mounted as an assembled unit behind a control panel, with an adjustment knob projecting through a hole in the panel.

A rotary shaft 10 is journaled into an annular case section 12 by means of a bushing 14 having a shoulder 16. The shaft and bushing are prevented from relative longitudinal movement by a retaining ring 18, while the shaft remains free to rotate. A flexible shaft 2%) is attached to shaft 10, leading to a coaxial female fitting 22 adapted to fasten onto any control to be adjusted by angular movement. The flexible shaft relieves the equipment manufacturer of the necessity of aligning the control assembly exactly with the unit to be adjusted.

A hub or rotatable member 28 surrounds shaft 10 and has a longitudinal bore 24 in which a compressible spring 26 is inserted at the end of the bore distant from the case section. The hub has two slots 36 extending longitudinally from the end closest to case section 12 part way toward the other end of the hub. The slots are located on opposite sides of the hub. A pin 32 pierces shaft 10 and engages the slots in the hub. In this manner, the hub may slide axially on the shaft, but is constrained to rotate with the shaft.

A knob 34 is fitted over the end of the hub and attached thereto. Spring 26 then forces the knob and hub away from shaft 10. The knob has serrations 36 on its outer surface for ease of rotation, and a central circular depression 38 as a convenient aid to pressing the knob with one finger while the others rotate it.

A Washer 40 surrounds the hub and rests against an annular flange or radial extension 41 on the hub. This washer serves as a fiat-surfaced clutching means and is made of a material with a high coeflicient of friction relative to the material of the hub and the material of the case in order to inhibit rotation when compressed between the two objects as will be shown below. Neoprene has been found to give satisfactory performance.

Another annular case section 42 is slid over the knob and attached to case section 12 by screws 44. This provides the rigid structure inside which the opposed spring force may bear, and furnishes a surface against which the washer bears when the knob is not pressed toward the shaft. Two microswitches 46 are attached to case section 42 by screws 48. These switches are actuated by very small motions against their contact points 50. The microswitches are provided with terminals 52 to which external circuitry may be connected by such means as leads 54. Any desired components may be connected to these leads, such as meters, which are ordinarily already in a disconnected circuit with the unit to be adjusted so that actuation of the switch serves to complete the circuit as discussed above.

Two leaf springs 56 are attached to case section 42 by screws 58, and bear against the flange, giving assistance to the spring 26 in urging the hub and the shaft apart. It is not desirable that leaf springs 56 exert much force, as they bear against the flange at a distance from the central axis, and create a very large moment, making it difiicult to turn the knob, even when depressed. The ends of the leaf springs are bent back (as shown in Fig. 1), and when the knob is axially depressed are flexed so their ends contact the actuating elements of the microswitches, thereby actuating the switches and incorporating the desired standardizing or measuring devices into the circuit.

Fig. 2 illustrates an example of the mechanical and electrical applications of this invention. A device, say a potentiometer 60 is mechanically connected to shaft 20 by means of fitting 22. This potentiometer as illustrated, is capable of varying the voltage drop across a resistance 62, both being connected in series to a voltage source 64. For purposes of illustration it is assumed that the voltage drop across the resistor is to be adjusted to a given value. A meter 66 is placed in a circuit with leads 54 and connected across the resistor whose potential drop is to be measured. When the device is unlocked, the microswitches will be actuated, and the circuit including lead 54 and meter 66 will be completed. Thus, as the knob is turned, adjusting the potentiometer, a meter reading showing the condition of the circuit element being adjusted is obtained. If desired, the leads from the other microswitch may be similarly connected elsewhere in the system to be adjusted along with any desired meters or standardized devices.

This assembly is a complete and self-contained unit which may be fastened onto any control panel. The same principles and similar designs may be used by attaching case section 12 directly to a panel, eliminating case section 42.

In operation, the technician need only press the knob, which releases the friction brake and permits rotation, and at the same time connects standard instruments into the circuit, turn the knob to the correct adjustment as shown by the instruments, and release the knob. The standard instruments are thus cut out of the circuit, and because of the locking means the adjustment cannot be disturbed without repeating the same procedure.

I claim:

1. In a control for an apparatus, the combination comprising an axially constrained rotatable shaft to be angularly adjusted, a rotatable member mounted in constant contact with the shaft such that the shaft and member are rotationally dependent but axially shiftable with respect to each other, means urging the shaft and member in opposite axial directions, a body at a fixed distance from the shaft having a hole larger than the member and through which the member projects, a radial extension on the member located between the body and the shaft, a piece of substance having a high coefficient friction relative to the body and the radial extension disposed between the radial extension and the body for inhibiting rotation at any angular position of the member when the member is forced toward the body, switching means, and means actuating the switching means when the member is forced away from the body.

2. In a control for an apparatus, the combination comprising an axially constrained rotatable shaft to be angularly adjusted, a rotatable member mounted in constant contact with the shaft such that the shaft and member are rotationally dependent but axially shiftable with respect to each other, means urging the shaft and member in opposite axial directions, a body at a fixed distance from the shaft having a hole larger than the member and through which the member projects, a shoulder on the member located between the body and the shaft, a piece of substance having a high coefficient friction relative to the body and the shoulder disposed between the shoulder and the body for inhibiting rotation at any angular position of the member when the member is forced toward the body, switching means, and means actuating the switching means when the member is forced away from the body.

3. In a control for an apparatus, the combination com prising an axially constrained rotatable shaft to be angularly adjusted, a rotatable member mounted in constant contact with the shaft such that the shaft and member are rotationally dependent but axially shiftable with respect to each other, means urging the shaft and member in opposite axial directions, a body at a fixed distance from the shaft having a hole larger than the member and through which the member projects, a radial extension on the member located between the body and the shaft, a Washer of a substance having a high coefficient of friction relative to the body and the radial extension disposed between the body and the radial extension for inhibiting rotation when the member is forced toward the body, switching means, and means actuating the switching means when the member is forced away from the body.

4. In a control for an apparatus, the combination comprising an axially constrained rotatable shaft to be angularly adjusted, a rotatable member mounted in constant contact with the shaft such that the shaft and member are rotationally dependent but axially shiftable with respect to each other, means urging the shaft and member in opposite axial directions, a body at a fixed distance from the shaft having a hole larger than the member and through which the member projects, a shoulder on the member located between the body and the shaft, a washer of a substance having a high coetficient of friction relative to the body and the shoulder disposed between the body and the radial extension between the shoulder and the body for inhibiting rotation when the member is forced toward the body, switching means, and means actuating the switching means when the member is forced away from the body.

5. In a control for an apparatus, the combination comprising an axially constrained rotatable shaft to be angularly adjusted, a rotatable member mounted in constant contact with the shaft such that the shaft and member are rotationally dependent but axially shiftable with respect to each other, means urging the shaft and member in opposite axial directions, a body at a fixed distance from the shaft having a hole larger than the member and through which the member projects, a shoulder on the member located between the body and the shaft, a washer of a substance having a high coefficient of friction relative to the body and the shoulder disposed between the body and the radial extension between the shoulder and the body for inhibiting rotation when the member is forced toward the body, switching means, and at least one contact member movable with respect to the rotatable member for actuating the switching means when the member is forced away from the body.

6. In a control for an apparatus, the combination comprising an axially constrained rotatable shaft to be angularly adjusted, a rotatable member mounted in constant contact with the shaft such that the shaft and member are rotationally dependent but axially shiftable with respect to each other, means urging the shaft and member in opposite axial directions, a body at a fixed distance from the shaft having a hole larger than the member and through which the member projects, a shoulder on the member located between the body and the shaft, a washer of a substance having a high coefficient of. Eric tion relative to the body and the shoulder disposed between the body and the radial extension between the shoulder and the body for inhibiting rotation when the member is forced toward the body, switching means for actuating an external circuit, and at least one contact member movable with respect to the rotatable member for actuating the switching means when the member is forced away from the body.

7. In a control for an apparatus, the combination comprising a case, an axially constrained rotatable shaft to be angularly adjusted mounted in the case, a rotatable mem' ber coaxially mounted on the shaft such that the shaft and member are rotationally dependent but axially shiftable with respect to each other, spring-loaded means between the shaft and the member urging them in axially opposite directions, the case having a hole larger than the member through which the member projects, a shoulder on the member located between the case and the shaft, a washer of a substance having a high coefficient of friction relative to the body and the shoulder disposed between the body and the shoulder for inhibiting rotation when the member is forced toward the case, switching means for actuating an external circuit, and at least one contact member movable with respect to the rotatable member for actuating the switching means when the member is forced toward the shaft.

References Cited in the file of this patent UNITED STATES PATENTS 2,451,224 Johnson Oct. 12, 1948 FOREIGN PATENTS 407,421 Great Britain Mar. 22, 1934 

